The present invention relates generally to a coffee grinder and coffee grinder controls, and more particularly, to a coffee grinder control circuit with a timer and two switches for uniquely controlling the operation of the coffee grinder.
A coffee grinder or coffee mill is an appliance that grinds roasted coffee beans, usually by use of an electrically operated motor. Coffee grinders are well known in the art, but the presently available controls for coffee grinders are generally lacking in safety, functionality and ease of use.
One prior art device, disclosed in U.S. Pat. No. 3,575,560 of Mayer et al, includes an electrically operated coffee grinder having a timer for controlling the length of time the grinder operates. The coffee grinder has a push button that protrudes through an opening in the coffee grinder housing. The push button is connected to a switch that is normally open and can be closed to energize a grinder motor and also is connected to a spring-driven timer mechanism. Depressing the push button closes the switch energizing the grind motor and also winds the spring of the timer mechanism, thereby setting the run time for the grinder. As the spring of the timer mechanism unwinds, the push button returns to its initial position and the grind motor is de-energized. The inner circumferential surface of the push button has a plurality of angularly-spaced grooves of varying lengths that can be placed into registry with a projection in the housing by a rotation of the push button about its longitudinal axis. The length of the grooves determines how far the push button can be depressed and corresponds to different lengths of grinding time as indicated by a scale on the push button. While the Mayer device has a coarse/fine selector switch, the switch is a separate device from a xe2x80x9cnumber-of-cupsxe2x80x9d setting on the pushbutton which is therefore an additional step for the user. Further, the Mayer device is electromechanical in nature, and therefore requires the user to pull-up a mechanism in order to stop the grinding operation instead of simply releasing a pushbutton or pressing a pushbutton. Additionally, there is no protection for a user who inadvertently opens the top or lid of the grinder during operation, which could be dangerous due to the fast moving blades and the potential for flying debris.
Another prior art device, disclosed in U.S. Pat. No. 4,607,200 of Zimmerman, includes a three-mode electric control circuit for a coffee grinder. The control circuit includes a grinder motor, a three-position control switch having xe2x80x9cOffxe2x80x9d, xe2x80x9cOnxe2x80x9d, and xe2x80x9cOn plus Startxe2x80x9d positions, a relay, and a timer. When the control circuit is in a first or xe2x80x9cOffxe2x80x9d mode, the switch is in the xe2x80x9cOffxe2x80x9d position and the circuit is completely de-energized. When the control circuit is in a second or xe2x80x9cStandbyxe2x80x9d mode, the switch is in the xe2x80x9cOnxe2x80x9d position and the circuit is partially energized such that a pulse from the timer will actuate and latch the relay. When the control circuit is in a third or xe2x80x9cRunxe2x80x9d mode, the timer has not timed-out, the relay is actuated and the motor is running. The switch is generally in the xe2x80x9cOnxe2x80x9d position when the control circuit is in the xe2x80x9cRunxe2x80x9d mode. However, the switch could also be in the momentary xe2x80x9cOn plus Startxe2x80x9d position if the immediately prior mode of the control circuit was the xe2x80x9cStandbyxe2x80x9d mode. A pivot located in the front panel of the grinder serves to actuate the three-position control switch. The Zimmerman device is primarily directed to large or commercial-type coffee grinders which have bag chutes (i.e., the lever) that activate the controls. However, there is no provision for a simple way to end a timed grind circuit by the release of a user operated pushbutton and there is no provision for a safety interlock switch to stop the grind operation in the event that the grinder lid or cover is opened.
What is needed, but not provided in the prior art, is a coffee grinder control circuit that will operate a coffee grinder for a user selectable period of time until the user releases one simple pushbutton, until a user push a simple pushbutton momentarily a second time, or until a safety interlock switch is opened by opening the lid of the coffee grinder.
Briefly stated, the present invention comprises a control circuit that controls a coffee grinder having a grinder motor. The control circuit includes a timer portion and a first switch. The first switch functions as a two-condition switch to place the control circuit in one of (1) an off condition when the first switch is open and the timer portion and the grinder motor are de-energized and (2) a run condition when the first switch is closed, the timer portion is energized, and the grinder motor is energized once in the run condition, the control circuit remaining in the run condition until the timer portion times out or until the first switch is re-opened thereby returning the control circuit to the off condition.
The present invention further comprises a control circuit that controls a coffee grinder having a grinder motor. The control circuit includes a timer portion, a first switch, and a second switch physically separated from the first switch. The switches together function as a two-condition switch to place the control circuit in one of (1) an off condition when one of the first switch and the second switch is open, the other switch is open or closed, and the timer portion and the grinder motor are de-energized and (2) a run condition when both the first and second switches are closed, the timer portion is energized, and the grinder motor is energized, once in the run condition, the control circuit remaining in the run condition until the timer portion times out or until one of the switches is re-opened thereby returning the control circuit to the off condition.
Further, the present invention comprises a control circuit that controls a coffee grinder having a grinder motor. The control circuit includes a timer portion, a safety interlock switch that is actuated to close when a lid on the coffee grinder is closed, and a pushbutton switch. The pushbutton switch is physically separated from the safety interlock switch which must be pushed and maintained by a user to energize the timer portion, and functions in conjunction with the safety interlock switch as a two-condition switch to place the control circuit in (1) an off condition when one of the safety interlock switch and the pushbutton switch is open, the other switch is open or closed, and the timer portion and the grinder motor are de-energized and (2) a run condition when both the safety interlock switch and the pushbutton switch are closed, the timer portion is energized, and the grinder motor is energized, once in the run condition, the control circuit remaining in the run condition until the timer portion times out or until one of the switches is re-opened thereby returning the control circuit to the off condition.
Alternatively, the pushbutton switch, still physically separated from the safety interlock switch, may need only be pushed momentarily by a user in order to energize the timer portion, and functions in conjunction with the safety interlock switch as a two-condition switch to place the control circuit in (1) an off condition when one of the safety interlock switch and the pushbutton switch is open, the other switch is open or closed, and the timer portion and the grinder motor are de-energized and (2) a run condition when both the safety interlock switch and the pushbutton switch are closed, the timer portion is energized, and the grinder motor is energized, once in the run condition, the control circuit remaining in the run condition until the timer portion times out or until the pushbutton is pushed momentarily a second time by the user in order to de-energize the control circuit, or until the safety interlock switch is re-opened thereby returning the control circuit to the off condition.